Crystal modification of C.I. Pigment Red 53:2 (δ-phase)

ABSTRACT

The invention relates to a novel crystal modification (δ-modification) of C.I. Pigment Red 53:2 of the formula (1) ##STR1## having the following characteristic reflections in the X-ray powder diffraction pattern: 
     
         ______________________________________                                    
 
    
     2Θ     d      relative intensity (in %)                             
______________________________________                                    
3.3          26.6   32                                                    
4.7          18.7   100                                                   
7.5          11.9   14                                                    
9.4          9.3    19                                                    
10.5         8.4    13                                                    
13.8         6.4    10                                                    
14.2         6.2    9                                                     
14.9         5.9    10                                                    
16.7         5.3    11                                                    
17.6         5.0    9                                                     
18.1         4.9    16                                                    
18.9         4.7    10                                                    
20.4         4.3    7                                                     
21.1         4.2    9                                                     
22.1         4.0    9                                                     
22.7         3.9    12                                                    
23.1         3.8    9                                                     
23.6         3.8    13                                                    
24.1         3.7    9                                                     
24.9         3.6    10                                                    
25.5         3.5    23                                                    
26.3         3.4    9                                                     
27.7         3.2    9                                                     
28.1         3.2    6                                                     
28.9         3.1    6                                                     
30.4         2.9    6                                                     
______________________________________

CROSS-REFERENCES TO RELATED APPLICATIONS

The present invention is described in the German priority applicationNo. 198 27 272.1 filed on Jun. 19, 1998, which is hereby incorporated byreference as is fully disclosed herein.

BACKGROUND OF THE INVENTION

C.I. Pigment Red 53:2 (below: P.R.53:2) is defined as the compound ofthe formula (I) which forms from the coupling of diazotized2-amino-5-chloro-4-methylbenzenesulfonic acid with β-naphthol andsubsequent reaction of the resulting sulfo acid with a calcium salt(M=1/2Ca²⁺). ##STR2##

In the solid state, the compound of the formula (I) may also be presentin another tautomeric or isomeric form and may also contain Na⁺ ions, Clions and/or water molecules.

Pigment Red 53 has long been known as a sodium salt (M═Na⁺). The bariumsalt, P.R.53:1, (M═Ba²⁺ /2), has long been produced in large amounts asa red pigment. It is used mainly in printing inks. The strontium salt(P.R.53:3) is of little commercial importance, as is the onlymodification of the calcium salt known to date (Pigment Red 53:2).

Most organic pigments exist in a plurality of different crystalmodifications, also referred to as "polymorphic forms". Crystalmodifications have the same chemical composition but a differentarrangement of the molecules in the crystal. The crystal structure mayinfluence the chemical and physical properties, and the individualcrystal modifications therefore often differ in the rheology, the colorand other coloristic properties. The crystal modifications can beidentified by X-ray powder diffractometry.

From P.R. 53:2 (M═Ca²⁺ /2), a crystal modification has been known todate which is referred to below as the α-modification. It isdistinguished by the following characteristic lines in the X-ray powderpattern (Cu--K.sub.α radiation, double diffraction angle, 2θ values indegrees, interplanar spacings d in A⁻¹, cf. FIG. 1):

    ______________________________________                                        α: 2Θ                                                                             d           Relative intensity in %                           ______________________________________                                               5.1  17.4        100                                                          6.6  13.4         73                                                          10.2 8.7          37                                                          12.2 7.2          39                                                          13.8 6.4          31, broad                                                   14.4 6.2          27, broad                                                   17.8 5.0          24, broad                                                   18.4 4.8          22                                                          20.4 4.4          20                                                          24.6 3.6          26                                                          25.8 3.4          86                                                   ______________________________________                                    

All line positions are associated with an uncertainty of ±0.2°.Depending on the crystal size and crystal quality, the lines at 13.8°and 14.4° may be fused into a broad line, as may be the lines at 17.8°and 18.4°.

SUMMARY OF THE INVENTION

The invention relates to a novel crystallographic modification(δ-modification) of C.I. Pigment Red 53:2. The invention also relates toa process for the preparation of the δ-modification of C.I. Pigment Red53:2.

DESCRIPTION OF THE DRAWINGS

FIG. 1. The crystal modification of C.I. Pigment Red 53:2 (α-phase).

FIG. 2. The crystal modification of C.I. Pigment Red 53:2 (δ-phase).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A novel crystal modification of P.R. 53:2, which is referred to as theδ-modification, has now surprisingly been found. It is distinguished bythe following characteristic lines (Cu--K.sub.α radiation, 2θ values indegrees, d values in Å⁻¹, cf. FIG. 2):

    ______________________________________                                        δ:                                                                             2Θ    d      Relative intensity (in %)                           ______________________________________                                        3.3            26.6   32                                                      4.7            18.7   100                                                     7.5            11.9   14                                                      9.4            9.3    19                                                      10.5           8.4    13                                                      13.8           6.4    10                                                      14.2           6.2    9                                                       14.9           5.9    10                                                      16.7           5.3    11                                                      17.6           5.0    9                                                       18.1           4.9    16                                                      18.9           4.7    10                                                      20.4           4.3    7                                                       21.1           4.2    9                                                       22.1           4.0    9                                                       22.7           3.9    12                                                      23.1           3.8    9                                                       23.6           3.8    13                                                      24.1           3.7    9                                                       24.9           3.6    10                                                      25.5           3.5    23                                                      26.3           3.4    9                                                       27.7           3.2    9                                                       28.1           3.2    6                                                       28.9           3.1    6                                                       30.4           2.9    6                                                       ______________________________________                                    

Here too, all line positions are associated with an uncertainty of±0.2°.

The relative intensities are usually influenced by preferred orientationand texture effects.

It is possible that some (up to 50%) of the Ca ions in the crystallattice of the crystal modification according to the invention arereplaced by other cations, e.g. Na⁺, H⁺, K⁺, NH₄ ⁺, Mg²⁺, Sr²⁺, Ba²⁺,Sn²⁺, Zn²⁺, Mn²⁺, Fe²⁺, Fe³⁺, Al³⁺, Si⁴⁺, Ti⁴⁺ or TiO²⁺. Suchcrystalline solid solutions can form if said other cations are alsopresent during the measures described below for the preparation of themodification according to the invention. Moreover, anions, such as, forexample, Cl⁻, and/or water molecules may be included in the crystallattice. However, it is preferable if 80% to almost 100% of M are Ca/2.

The invention therefore relates to C.I. Pigment Red 53:2 of the aboveformula (I), in which M is a cation, with the proviso that at least 50%of the cations are calcium ions, in the δ-modification, which has theabovementioned characteristic reflections in the X-ray powderdiffraction pattern.

The δ-modification is slightly soluble, has high color strength and isdistinguished by brilliant, orange colorations.

The invention also relates to a process for the preparation of theδ-modification of C.I. Pigment Red 53:2 by reacting β-naphthol with thediazonium salt of the formula (2) ##STR3## in which M¹ is hydrogen or acation equivalent, such as, for example, Na, K, 1/2 Mg, 1/3 Al, 1/2 Znor NH₄ ;

and X is an anion or anion equivalent, such as, for example, Cl⁻, 1/2SO₄ ²⁻, HSO₄ ⁻, NO₃ ⁻ or CH₃ COO⁻ ;

and a calcium salt, for example CaCl₂, Ca(NO₃)₂, Ca acetate, Ca(HCO₃)₂,CaCO₃, CaO or Ca(OH)₂, in the presence of chlorobenzene.

The reaction can usually be carried out at temperatures of from 0° C. to200° C., preferably from 20° C. to the boiling point of said solvent, atatmospheric pressure.

The crystal modification according to the invention is also obtained ifC.I. Pigment Red 53:2 which is present wholly or partly in theα-modification is heated together with chlorobenzene or achlorobenzene/water mixture to a temperature of from 40 to 200° C.,preferably from 60° C. to the boiling point of the solvent or solventmixture, at atmospheric pressure, the pigment partly or wholly goinginto solution, and is then reprecipitated, for example by reducing thetemperature to from -20 to ±90° C. and/or by adding water and/or asecond solvent having a lower dissolving power and/by changing the pHand/or by adding a salt, such as, for example, NaCl.

The chlorobenzene/water mixture used for dissolution or partialdissolution at elevated temperature may contain up to 95% by weight ofwater. Heating may be carried out at atmospheric pressure, at reducedpressure or at superatmospheric pressure.

For example, benzene, toluene or alkanes are suitable as a secondsolvent. The change in the pH can be brought about by adding acids orbases. The P.R. 53:2 used as starting material may be employed as a drypigment, in the form of a water-moist press cake, as a solution or as anaqueous suspension. The duration of the solvent treatment described maybe from 10 seconds to 24 hours, preferably from 10 minutes to 2 hours.In order to obtain the crystal modification according to the invention,it is expedient subsequently to reduce the temperature to a value in therange between 20 and 80° C., preferably in the course of from 5 minutesto 2 hours.

The P.R. 53:2 according to the invention and of the δ-modification canbe isolated at elevated temperature or after cooling, for example toroom temperature, in the conventional manner, for example by filteringoff or by evaporating the solvent, if necessary with application of avacuum. It may be expedient to wash the press cake or residue withwater, an organic liquid, for example a lower alcohol, such as methanol,ethanol, propanol or isopropanol, or with acetone.

Depending on the desired field of use, it may be useful to subject thepigment obtained to fine mechanical comminution. The fine comminutioncan be effected by wet or dry milling. The milling may be followed by atreatment with a solvent, with water or with a solvent/water mixture inorder to convert the pigment into a ready-to-use form.

The crystal modification according to the invention is also obtained ifC.I. Pigment Red 53:2 which is present wholly or partly in theα-modification is kneaded or milled in the presence of chlorobenzene ora chlorobenzene/water mixture. The kneading or milling can be carriedout at a temperature of from 40 to 200° C., preferably from 60° C. tothe boiling point of the solvent chosen, at atmospheric pressure.

Depending on the composition of the chlorobenzene-containing mixture, onthe concentration, on the temperature used, on the pressure, on thecooling rate of the solution and on the presence of seed crystals, thepure δ-phase or a mixture of α- and δ-phase may form.

The pure or predominantly pure δ-modification is preferably formed if asolution in which seed crystals or crystal nuclei of the δ-modificationare already present is used as the starting material and if thissolution is cooled so slowly, or a second, more poorly dissolvingsolvent, an acid, a base or a salt is added so slowly, thatsupersaturation is kept in a range in which the crystal growth rate isrelatively high but the rate of formation of crystal nuclei isrelatively low, so that the crystal nuclei present grow while themodification is maintained. The use of a mechanical stirrer may beadvantageous since it breaks up existing crystals of the δ-modificationinto many smaller fragments which then in turn serve as crystal nucleifor the δ-modification (so-called secondary nucleation). If thesupersaturation is higher, for example because the solution is cooledmore rapidly or a second solvent, an acid, a base or a salt is addedmore rapidly, the rate of formation of crystal nuclei is higher so thatmany crystal nuclei of the α- and δ-modification may form spontaneously;this generally gives mixtures of modifications which only partlycomprise the δ-modification.

The preparation of a mixture of the α- and δ-modification may be ofinterest if specific coloristic and rheological properties are desired,for example a specific orange hue outside or between the orange-redα-modification and the orange δ-modification. On the other hand, it isalso possible to concentrate a mixture of δ-modification andα-modification in order to obtain a higher δ-fraction or the pureδ-modification, for example by a air classification, recrystallization,selective dissolution or extraction of the α-modification or by repeateduse of process measures according to the invention, in which theformation of the δ-modification is favored.

The present invention therefore also relates to a C.I. Pigment Red 53:2mixture which contains at least 10%, preferably at least 25%, inparticular at least 50%, particularly preferably at least 75%, of theδ-modification.

To facilitate the change of modification, to stabilize theδ-modification, to improve the coloristic properties and/or to achievespecific coloristic effects, pigment dispersants, surfactants,antifoams, extenders or other additives may be added at any desiredpoints in the process. Mixtures of these additives may also be used. Theadditives may be added all at once or in a plurality of portions. Theadditives may be added at any point during the synthesis or during thevarious treatments (heating with a solvent or in water,recrystallization, milling, kneading) or after the aftertreatments. Themost suitable time must be determined beforehand by exploratoryexperiments.

The C.I. Pigment Red 53:2 according to the invention, in theδ-modification, or mixtures which contain the δ-modification, or thedescribed crystalline solid solutions of the δ-modification with othercations are suitable for pigmenting coatings and plastics, for theproduction of printing inks and aqueous pigment preparations and forcoloring seeds.

The δ-modification according to the invention, said mixtures and saidcrystalline solid solutions are also suitable as colorants inelectrophotographic toners and developers, such as, for example, one- ortwo-component powder toners (also referred to as one- or two-componentdevelopers), magnetic toners, liquid toners, polymerization toners andspecial toners.

Typical toner binders are polymer resins, polyaddition resins andpolycondensation resins, such as styrene, styrenelacrylate,styrene/butadiene, acrylate, polyester or phenol/epoxide resins,polysulfones or polyurethanes, individually or in combination, andpolyethylene and polypropylene, which may contain further ingredients,such as charge controlling agents, waxes or flow assistants, or aresubsequently modified with these additives.

Furthermore, the δ-modification according to the invention or one ofsaid mixtures or crystalline solid solutions is suitable as a colorantin powders and powder coatings, in particular triboelectrically orelectrokinetically sprayable powder coatings, which are used for thesurface coating of articles of, for example, metal, wood, plastic,glass, ceramic, concrete, textile material, paper or rubber.

Typically used powder coating resins are epoxy resins, polyester resinscontaining carboxyl and hydroxyl groups, and polyurethane and acrylateresins, together with conventional curing agents. Combinations of resinsare also used. Thus, for example, epoxy resins are frequently used incombination with polyester resins containing carboxyl and hydroxylgroups. Typical curing components (depending on the resin system) are,for example, acid anhydrides, imidazoles and dicyandiamide and theirderivatives, blocked isocyanates, bisacylurethanes, phenol resins andmelamine resins, triglycidyl isocyanurates, oxazolines and dicarboxylicacids.

Moreover, the δ-modification according to the invention or one of saidmixtures and crystalline solid solution are suitable as colorants inaqueous and nonaqueous inkjet inks and in those inks which operateaccording to the hot melt method. Furthermore, the δ-modificationaccording to the invention or one of said mixtures and crystalline solidsolutions are suitable as colorants for color filters and for additiveas well as subtractive color production.

In the following examples, parts and percentages are based on weight.The crystal modification of the products obtained is carried out byX-ray powder diffractometry (Cu--K.sub.□ radiation).

EXAMPLES

1) Addition of Chlorobenzene During the Laking

a) Diazotization and coupling:

226 parts of 2-amino-4-methyl-5-chlorobenzenesulfonic acid are stirredwith 2500 parts of water and 150 parts of 31% strength hydrochloric acidat room temperature. At 20-25° C., diazotization is effected with 173parts of 40% strength NaNO₂ solution in the course of 30 minutes andstirring is continued for 1 hour at room temperature. 150 parts ofβ-naphthol are dissolved in 1100 parts of 4% strength NaOH and added tothe diazo suspension at room temperature in the course of 60 minutes.

b) Laking in the presence of chlorobenzene:

The pH of the suspension is adjusted to 8.0 with NaOH, and 480 parts ofchlorobenzene and 76 parts of CaCl₂ are added. The chlorobenzene isdistilled off by passing in steam (at atmospheric pressure). The mixtureis filtered while hot. The press cake is washed with cold water anddried at 60° C. 400 parts of P.R. 53:2 in the δ-modification areobtained.

2) Addition of Chlorobenzene After the Laking

The diazotization and coupling are carried out as in Example 1. The pHof the suspension from Example 1a) is adjusted to 8.0 with NaOH, and 61parts of CaCl₂ and 500 parts of water are added. The mixture is stirredfor 15 minutes at 95° C. 2400 parts of chlorobenzene are added to thesuspension at 80° C. and the mixture is refluxed for 2 hours (88-90° C).The chlorobenzene is distilled off with steam; the mixture is filteredand the residue is washed with water and dried at 60° C. 408 parts ofP.R. 53:2 in the δ-modification are obtained.

3) Treatment of the Press Cake with Chlorobenzene

The diazotization and coupling are carried out as in Example 1. The pHof the suspension from Example 1a) is adjusted to 8.0 with NaOH, and 61parts of CaCl₂ and 500 parts of water are added. The suspension isstirred for 15 minutes at 95° C. and filtered while hot and the presscake is washed salt-free. 1534 parts of press cake are obtained. 128parts of this press cake are stirred with 332 parts of water and 200parts of chlorobenzene and refluxed for 2 hours (88-90° C.). Thechlorobenzene is distilled off with steam, the mixture is filtered andthe residue is washed with water and dried at 60° C. 30 parts of P.R.53:2 in the δ-modification are obtained (cf. FIG. 2).

What is claimed is:
 1. A C.I. Pigment Red 53:2 of the formula (I)##STR4## in which M is a cation, with the proviso that at least 50% ofthe cations are calcium ions,in the δ-modification, which has thefollowing characteristic reflections in the X-ray powder diffractionpattern, measured using Cu--K.sub.α radiation:

    ______________________________________                                        δ:                                                                             2Θ    d      relative intensity (in %)                           ______________________________________                                        3.3            26.6   32                                                      4.7            18.7   100                                                     7.5            11.9   14                                                      9.4            9.3    19                                                      10.5           8.4    13                                                      13.8           6.4    10                                                      14.2           6.2    9                                                       14.9           5.9    10                                                      16.7           5.3    11                                                      17.6           5.0    9                                                       18.1           4.9    16                                                      18.9           4.7    10                                                      20.4           4.3    7                                                       21.1           4.2    9                                                       22.1           4.0    9                                                       22.7           3.9    12                                                      23.1           3.8    9                                                       23.6           3.8    13                                                      24.1           3.7    9                                                       24.9           3.6    10                                                      25.5           3.5    23                                                      26.3           3.4    9                                                       27.7           3.2    9                                                       28.1           3.2    6                                                       28.9           3.1    6                                                       30.4           2.9   
 6.                                                      ______________________________________                                    


2. The C.I. Pigment Red 53:2 as claimed in claim 1, wherein from 80% toalmost 100% of M are calcium.
 3. The C.I. Pigment Red 53:2 as claimed inclaim 1, wherein M is one or more cations Na⁺,H⁺,K⁺,NH₄⁺,Mg²⁺,Sr²⁺,Ba²⁺,Sn.sup.2+,Zn²⁺,Mn²⁺,Fe²⁺,Fe³⁺,Al³⁺, Si⁴⁺,Ti⁴⁺ or TiO²⁺,in addition to calcium.
 4. A process for the preparation of C.I. PigmentRed 53:2 of the formula (I) ##STR5## in which M is a cation, with theproviso that at least 50% of the cations are calcium ions,in theδ-modification, which has the following characteristic reflections inthe X-ray powder diffraction pattern, measured using Cu--K.sub.αradiation:

    ______________________________________                                        δ:                                                                             2Θ    d      Relative intensity (in %)                           ______________________________________                                        3.3            26.6   32                                                      4.7            18.7   100                                                     7.5            11.9   14                                                      9.4            9.3    19                                                      10.5           8.4    13                                                      13.8           6.4    10                                                      14.2           6.2    9                                                       14.9           5.9    10                                                      16.7           5.3    11                                                      17.6           5.0    9                                                       18.1           4.9    16                                                      18.9           4.7    10                                                      20.4           4.3    7                                                       21.1           4.2    9                                                       22.1           4.0    9                                                       22.7           3.9    12                                                      23.1           3.8    9                                                       23.6           3.8    13                                                      24.1           3.7    9                                                       24.9           3.6    10                                                      25.5           3.5    23                                                      26.3           3.4    9                                                       27.7           3.2    9                                                       28.1           3.2    6                                                       28.9           3.1    6                                                       30.4           2.9    6                                                       ______________________________________                                    

wherein β-naphthol is reacted with the diazonium salt of the formula (2)##STR6## in which M¹ is hydrogen or a cation equivalent and X is ananion and with a calcium salt in the presence of chlorobenzene.
 5. Theprocess as claimed in claim 4, wherein X is chloride, sulfate, hydrogensulfate, nitrate or acetate.
 6. The process as claimed in claim 4,wherein the calcium salt is CaCl₂, Ca(NO₃)₂, CaCO₃, Ca(HCO₃)₂, Caacetate, CaO or Ca(OH)₂.
 7. The process as claimed in claim 4, whereinthe reaction is carried out at a temperature of from 0 to 200° C.
 8. Theprocess as claimed in claim 4, wherein the reaction is carried ot at atemperature of from 20° C. to the boiling point of the chlorobenzene atatmospheric pressure.
 9. A process for the preparation of C.I. PigmentRed 53:2 of the formula (I) ##STR7## in which M is a cation, with theproviso that at least 50% of the cations are calcium ions,in theδ-modification, which has the following characteristic reflections inthe X-ray powder diffraction pattern, measured using Cu--K.sub.αradiation:

    ______________________________________                                        δ:                                                                             2Θ    d      Relative intensity (in %)                           ______________________________________                                        3.3            26.6   32                                                      4.7            18.7   100                                                     7.5            11.9   14                                                      9.4            9.3    19                                                      10.5           8.4    13                                                      13.8           6.4    10                                                      14.2           6.2    9                                                       14.9           5.9    10                                                      16.7           5.3    11                                                      17.6           5.0    9                                                       18.1           4.9    16                                                      18.9           4.7    10                                                      20.4           4.3    7                                                       21.1           4.2    9                                                       22.1           4.0    9                                                       22.7           3.9    12                                                      23.1           3.8    9                                                       23.6           3.8    13                                                      24.1           3.7    9                                                       24.9           3.6    10                                                      25.5           3.5    23                                                      26.3           3.4    9                                                       27.7           3.2    9                                                       28.1           3.2    6                                                       28.9           3.1    6                                                       30.4           2.9    6                                                       ______________________________________                                    

wherein C.I. Pigment Red 53:2 which is present wholly or partially inthe α-modification is heated, together with chlorobenzene or achlorobenzene/water mixture, to a temperature of from 40 to 200° C., andthen cooled to a temperature of from -20 to +90° C., optionally water, asecond solvent having low dissolving power or a combination thereof areadded and, optionally, an acid, an alkali or a salt is added.
 10. Theprocess as claimed in claim 9, wherein C.I. Pigment Red 53:2 which ispresent wholly or partially in the α-modification is heated, togetherwith chlorobenzene or a chlorobenzene/water mixture, to a temperature offrom 60° C. to the boiling point of the solvent or solvent mixture atatmospheric pressure, and then cooled to a temperature of from -20 to+90° C., optionally water, a second solvent having low dissolving poweror a combination thereof are added and, optionally, an acid, an alkalior a salt is added.
 11. The process as claimed in claim 9, wherein theC.I. Pigment Red 53:2 which is present wholly or partly in theα-modification is used as a dry pigment, in the form of a water-moistpress cake or as an aqueous suspension.
 12. A process for thepreparation of C.I. Pigment Red 53:2 of the formula (I) ##STR8## inwhich M is a cation, with the proviso that at least 50% of the cationsare calcium ions,in the δ-modification, which has the followingcharacteristic reflections in the X-ray powder diffraction pattern,measured using Cu--K.sub.α radiation:

    ______________________________________                                        δ:                                                                             2Θ    d      Relative intensity (in %)                           ______________________________________                                        3.3            26.6   32                                                      4.7            18.7   100                                                     7.5            11.9   14                                                      9.4            9.3    19                                                      10.5           8.4    13                                                      13.8           6.4    10                                                      14.2           6.2    9                                                       14.9           5.9    10                                                      16.7           5.3    11                                                      17.6           5.0    9                                                       18.1           4.9    16                                                      18.9           4.7    10                                                      20.4           4.3    7                                                       21.1           4.2    9                                                       22.1           4.0    9                                                       22.7           3.9    12                                                      23.1           3.8    9                                                       23.6           3.8    13                                                      24.1           3.7    9                                                       24.9           3.6    10                                                      25.5           3.5    23                                                      26.3           3.4    9                                                       27.7           3.2    9                                                       28.1           3.2    6                                                       28.9           3.1    6                                                       30.4           2.9    6                                                       ______________________________________                                    

wherein C.I. Pigment Red 53:2 which is present wholly or partly in theα-modification is kneaded or milled in the presence of chlorobenzene ora chlorobenzene/water mixture at a temperature of from 40 to 200° C. 13.A C.I. Pigment Red 53:2 mixture containing at least 10% of theδ-modification as claimed in claim
 1. 14. The mixture as claimed inclaim 13, containing at least 25% of the δ-modification.
 15. The mixtureas claimed in claim 13, containing at least 50% of the δ-modification.16. The mixture as claimed in claim 13, containing at least 75% of theδ-modification.
 17. A method of pigmenting coatings, plastics, printinginks, electrophotographic toners and developers, powder coatings, inkjetinks, aqueous pigment preparations and seeds comprising the step ofadding a C.I. Pigment Red 53:2 of the formula (I) ##STR9## in which M isa cation, with the proviso that at least 50% of the cations are calciumions,in the δ-modification, which has the following characteristicreflections in the X-ray powder diffraction pattern, measured usingCu--K.sub.α radiation:

    ______________________________________                                        δ:                                                                             2Θ    d      Relative intensity (in %)                           ______________________________________                                        3.3            26.6   32                                                      4.7            18.7   100                                                     7.5            11.9   14                                                      9.4            9.3    19                                                      10.5           8.4    13                                                      13.8           6.4    10                                                      14.2           6.2    9                                                       14.9           5.9    10                                                      16.7           5.3    11                                                      17.6           5.0    9                                                       18.1           4.9    16                                                      18.9           4.7    10                                                      20.4           4.3    7                                                       21.1           4.2    9                                                       22.1           4.0    9                                                       22.7           3.9    12                                                      23.1           3.8    9                                                       23.6           3.8    13                                                      24.1           3.7    9                                                       24.9           3.6    10                                                      25.5           3.5    23                                                      26.3           3.4    9                                                       27.7           3.2    9                                                       28.1           3.2    6                                                       28.9           3.1    6                                                       30.4           2.9    6                                                       ______________________________________                                    

to a coating, plastic, printing ink liquor, electrophotographic tonerand developer, powder coating, inkjet ink liquor, aqueous pigmentpreparation or seed to be pigmented.